Sea Slug feeding and babies

Dear Andrew,
I am pretty sure that your sea slugs are Sea Hares. If you go to that page you will find plenty of information on them and links to other pages on the Forum with stuff on Sea Hares.

Some species flap their the wing-like 'parapodia' to swim, but from your description, your animals are really just drifting in the currents. I suspect the species you have is Aplysia juliana which ranges in colour from pale brown to black and often has whitish patches on the body. Most sea hares produce a purple ink if they are disturbed. A. juliana is one of the few species that does not, so if your animals do produce purple ink let me know and I'll rethink my identification.

On food. Most species change their algal food during their life cycle. Your animals are apparently thriving Ulva - the Green Sea Lettuce, so I would leave them on that as other algae often foul aquarium water by excreting toxic chemicals. If you run out of sea lettuce one correspondent to the Forum said they used ordinary lettuce to feed sea hares.

The change in colour of the eggs (or rather the developing larvae/embryo) is quite normal. You will know when the larvae hatch because you will have swarms of tiny veliger larvae swimming in the aquarium and probably getting stuck in the surface film. Without special equipment it is unlikely that you can keep the free swimming larvae alive and feeding in aquarium conditions. How long will your adults live? In the wild they are only likely to survive a few months and definitely leass than a year. In aquaria things tend to live a bit longer but if they do die it's probably because of their age not the way you are looking after them.

Best wishes,
Bill Rudman.